[Python-Dev] PEP 3151 from the BDFOP (original) (raw)

Barry Warsaw barry at python.org
Mon Aug 29 23:21:05 CEST 2011

On Aug 24, 2011, at 12:51 PM, Nick Coghlan wrote:

On Wed, Aug 24, 2011 at 9:57 AM, Antoine Pitrou <solipsis at pitrou.net> wrote:

Using IOError.new is the easiest way to ensure that all code raising IO errors takes advantage of the errno mapping. Otherwise you may get APIs raising the proper subclasses, and other APIs always raising base IOError (it doesn't happen often, but some Python library code raises an IOError with an explicit errno). It's also the natural place to put the errno->exception type mapping so that existing code will raise the new errors without requiring modification. We could spell it as a new class method ("fromerrno" or similar), but there isn't any ambiguity in doing it directly in new, so a class method seems pointlessly inconvenient.

As I mentioned, my main concern with this is the surprise factor for people debugging and reading the code. A class method would solve that, but looks uglier and doesn't work with existing code.

-Barry

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